Electric tubular heater terminal seal



Nov. 29, 1949 A. P. CHARBONNEAU ETYAL 2,489,998

ELECTRIC TUBULAR HEATER TERMINAL SEAL Filed Jan. 8, 1948 GU/g3: Z,

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FUSLON H F WELD USION m 1 v WELD w i 6 w in 1' I5- I I1 ll 1 2- lPatented Nov. 29,1949

UNITED STATES PATENT OFFICE ELECTRIC TUBULQR HEATER TERMINAL wareApplication January 8, 1948, Serlal No. 1,146

This invention relates to electric heaters and more particularly to animproved method of and means for sealing terminals of heaters havingtubular enclosing sheaths.

An object of the present invention is to provide for making a highlysatisfactory terminal seal for tubular sheathed heaters in a simple andexpeditious manner.

Another object is to provide a terminal seal which is impervious tomoisture and of a nonbreakable character;

Another object is to provide a terminal seal of the aforementionedcharacter without the application of heat or introduction of fusiblesealing materials.

Other objects and advantages of the invention will hereinafter appear.

The accompanying drawings illustrate an embodiment of the inventionwhich will now be described. r

In the drawings:

Figure 1 is a view in longitudinal section of a portion of a tubulartype heater prior to the application of a terminal seal.

Fig. 2 is like Fig. 1, but shows the terminal seal in a completed state,and

Fig. 3 is like Fig. 2, but modified in respect of the terminal sealretaining member.

Referring to Fig. 1 it shows a tubular type electric heater comprising ahelical resistor 5 which 4; Claims. (CL 201-41) so that its inner endengages the insulating material I. Then a locking member II, which inone preferred form is a blade-dike terminal device shown in Fig. 2, isattached to the extended end of terminal lead 8 as by fusion welding. Toaii'ord proper sealing action by the plug I0 it is necessary that memberl2, during and following its attachment to the terminal lead 8 in anypreferred manner compress the plug Ill inwardly of the recess 9 toeffect longitudinal compression of the plug. Such compression Of theplug Io provides for lateral expansion of the same within recess 9 toeflect intimate and tightly fitting engagement is embedded in acompacted mass of refractory insulating material 6 and incased by atubular metal sheath 1 of any preferred cross sectional form. Theresistor 5 is connected in any preferred manner to a terminal lead 8which extends outwardly of the sheath 1. The sheath adjacent its end isunfilled and provides a recess 9 to receive the terminal seal.

Prior to applying the terminal seal, it is assumed that the heater hasbeen worked as by swaging to the desired cross sectional form anddimensions.

A plug i0 composed of silicone rubber of elastic character, such as, forexample, Dow Corning Silastic No. 180, is used for effecting a terminalseal. Preferably plug I0 is externally formed to match the crosssectional form of the recess 9 but with slightly smaller dimensions tofacilitate its insertion within recess 9. It is also provided with acentral longitudinal perforation H to provide clearance for terminallead 8. The length of plug in is preferably somewhat in excess of thedepth of recess 9.

To effect the terminal seal, plug I0 is slipped onto terminal lead 8 andis inserted into re$$ 9 66 1.

of the plug with the inner walls of sheath I and with the terminal lead8.

As shown in Fig. 2, a washer i3 is preferably interposed between theadjacent ends of plug iii and member I! to insure that when the latteris attached to terminal lead 8 it will exert pressure on plug Illsubstantially uniformly about the outer end of the latter. However,washer is may be dispensed with as desired when-other preferred lockingmembers or terminal devices are used which are provided with abuttingend portions that substantially overlie the end of the plug; such as forexample another preferred type of terminal device I shown in Fig. 3.

If the terminal seal has been eflected as hereinbefore described afinished terminal such as shown in Figs. 2 and 3 will be had. Theterminal seal will be moisture impervious and of a nonbreakablecharacter. The use of a silicone rubber plug as the sealing mediuminsures that the seal will not disintegrate unless the temperature ofthe terminal end of the heater exceeds 500' Fahrenheit. The terminal endtemperatures of properly designed and constructed tubular sheathedheaters such as used in the cooking art are substantially below 500Fahrenheit even when subjected to their maximum rated wattages. Thedanger of seal disintegration due to heat is therefore remote.

It will be apparent that the terminal seal described herein has numerousadvantages. The use of fusible sealing materials is obviated, andseveral steps heretofore used in providing a finished terminal seal areeliminated. Consequently there is a saving in time and cost. Because ofthe elastic character of the seal it is not subject to breakage which isordinarily associated with many types of terminal seals heretofore used.

What we claim as new and desire to secure by Letters Patent is:

The method of sealing the terminal end of an electric heater wherein aresistor enclosed in an open end tubular sheath is embedded in insulation at a distance from the end of the sheath to leave the sheathwith an open end recess, and wherein the resistor has a terminal portionprojecting through such recess to a point beyond the sheath, comprisingthe step of inserting a perforated heat resistant plug of elasticcharacter into the open end recess of said heater, compressing said pluginwardly of said recess to cause lateral expansion of said plug forengagement with the inner walls of said sheath and with said terminalportion of said resistor, and locking a member to said terminal portionof said resistor toretain said plug in compressed condition.

2. The method of sealing the terminal end of an electric heater whereina resistor enclosed in an open end tubular sheath is embedded ininsulation at a distance from the end of the sheath to leave the sheathwith an open end recess, and wherein the resistor has a terminal portionprojecting through such recess to a point beyond the sheath, comprisingthe steps of slipping onto the terminal portion of said resistor aperforated silicone rubber plug of elastic character, inserting saidplug into the open end recess of said heater, compressing said pluginwardly of said recess to cause lateral expansion of said plug forengagement with the inner walls of said sheath and with said terminalportion of said resistor, and looking a member to said terminal portionof said resistor to retain said plug in compressed condition.

3. The combination with a tubular heater comprising a resistor having aterminal portion, an open end tubular sheath surrounding said resistorand also its terminal portion in part, and insulation in said sheathretaining said resistor in spaced relation to said sheath, saidinsulation terminating at a distance from the end of said sheath leavingsaid sheath with an open end recess through which said terminal portionprojects, of a perforated elastic plug formed of heat resistant materialcompressed in situ to tightly engage said insulation, the inner walls ofsaid sheath and the terminal portion of said resistor projecting throughsaid recess, and a member locked to said terminal portion of saidresistor to maintain said plug in such compressed state.

4. The combination with a tubular heater comprising a resistor having aterminal portion, an open end tubular sheath surrounding said resistorand also its terminal portion in part, and insulation in said sheathretaining said resistor in spaced relation to said sheath, saidinsulation terminating at a distance from the end of said sheath,leaving said sheath with an open end recess through which said terminalportion projects, of a perforated silicone rubber plug of elasticcharacter compressed in situ to tightly engage said insulation, theinner walls of said sheath and the terminal portion of said resistorprojecting through said recess, and a member locked to said terminalportion of said resistor to maintain said plug in such compressed state.

ALLAN P. CHARBONNEAU. EDWIN SEEGER.

REFERENCES CETED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS Number Name Date 2,003,175 Daly May 28, 19352,369,045 Hampton et a1 Feb. 6, 1945 2,375,058 Wiegancl May 1, 19452,397,568 Seaman Apr. 2, 1946 2,428,053 Vasileff Sept. 30, 1947 AFOREGN' PATENTS Number Country Date 495,212 Great Britain Nov. 9, 1938OTHER. REFERENCES Knight, Silicones, October 1945, pages 1069- 1073 ofMaterials And Methods.

Silicones, April 22, 1946, pages 121-122, Steel.

